How to use app/callbacks/server hooks from an App?

Is it possible to add to or invoke the app/callbacks/server/index.js hooks from a Rocket.Chat App? Or any other approach other than forking Rocket.Chat?

There’s a callback hook for filtering departments that would be absolutely perfect for a use case I have, if I could add my own custom logic to the callback to run when invoked. Unfortunately, Rocket.Chat enterprise’s units functionality doesn’t satisfy this as the filtering logic I need to run is very niche.

If there was some way to just perform a callback.add() from a Rocket.Chat App?